The present invention relates to the field of the landing of aircraft on a landing runway.
The effectiveness of aircraft braking on the landing runway depends on the state of the runway. The state of the landing runway depends on meteorological conditions. Examples of runway states include: dry, wet (rain), snow and ice.
Patent application FR2.930.669 discloses a device onboard an aircraft for identifying the state of a landing runway on which this aircraft is landing.
During trials of a new aircraft, the aircraft's braking performance is generally tested by landing the aircraft on runways under different runway states, such as a “dry runway” and a “wet runway.” The tests are used to create models of the aircraft's braking performance for different runway states. The braking performance of the aircraft on runways under other states is customarily estimated on the basis of the models.
It would be helpful to actually measure the braking performance for all possible runway states during actual braking of the aircraft. It is generally easy to find a landing runway corresponding to a “dry runway” state, and even a wet runway state to measure actual braking performance. To actually measure braking performance on runways under other states, such as snow or ice, it would require taking the aircraft to a geographical location at which the meteorological conditions allow the presence of snow or ice.
To measure braking performance on all runway states would be expensive and time consuming, especially as compared to measuring braking performance on only dry and wet runway states. Moreover, one cannot be certain that the state of the runway would be homogeneous over the whole of the length of the landing runway. Neither would one be certain that the actual state of the runway would correspond to the conditions of the lowest possible adhesion of the wheels of the aircraft to the runway for all runway states.